<!DOCTYPE html>
<html>
<head>
<script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.js"></script>
</head>
<body>
<ul id="one" class="level-1">
  <li class="item-i">I</li>
  <li id="ii" class="item-ii">II
  <ul class="level-2">
    <li class="item-a">A</li>
    <li class="item-b">B
      <ul class="level-3">
        <li class="item-1">1</li>
        <li class="item-2">2</li>
        <li class="item-3">3</li>
      </ul>
    </li>
    <li class="item-c">C</li>
  </ul>
  </li>
  <li class="item-iii">III</li>
</ul>
<script>
var listItemII = document.getElementById('ii');
// $('li.item-a').closest('ul', listItemII).css('background-color', 'red');
$('li.item-a').closest('ul', listItemII).css('background-color', 'green');
</script>
</body>
</html>
